A Novel Virtue in Stem Cell Research: Exosomes and Their Role in Differentiation.

In the past decade a number of different stem cell types have entered the clinical applications increasingly as a therapeutic option, due to their tissue maintenance capacity at the site where they localize. Although it was initially thought that conferral of resilience to damaged tissue largely depends on the stem cells themselves through orchestration of signaling among the local epithelial and immune systems at the injury site, recent findings point out that the remarkable regenerative capacity of stem cells is rather due to their nanovesicular products that emerge as the new active players of tissue repair processes. Among these extracellular vesicles exosomes generated particularly by stem cells have been receiving a substantial interest both in the fields of stem cell biology and extracellular vesicles. In this chapter fundamental facts about stem cell biology, biogenesis of extracellular vesicles and exosomes, their structure, and function are summarized. Moreover, properties of both tumor-derived exosomes as well as those derived from stem cells are discussed relatively in-depth in terms of their influence on proximal and distal tissue physiology. Last but not the least, among countless studies in an exploding field, we summarize those that attempt to unravel the complex signaling networks through which stem cell-derived exosomes alter the fate of differentiating stem cells as well as the molecular make-up of exosomes released from differentiating stem cells by conducting thorough proteomic and genomic analyses with the ultimate goal of identifying effector gene products mediating exosomal cues in stem cell biology.